Environmental Geochemistry and Health 1993 15(1) page 51
Oxidisability of environmental sulphur under different catalytic conditions Namrata Shukla and G,S, Pandey*
Department of Chemistry, Ravishankar University, Raipur, M.P. 492 010, India Abstract The oxidation of elemental sulphur in the catalytic presence of selected metal ions [Cr(lll), Ce(lll), Cu(ll), Hg(ll), Ni(ll), Co(ll), Mo(Vl), Cd(ll), Zn(ll), Ti(IV), and V(V)], and hydrocarbons (benzene, gasoline, and kerosene) was studied in an alkaline medium buffered by marble powder. The catalytic efficiencies of metal ions were: Cr(lll) > Ce(lll) > Cu(ll) > Hg(ll > Ni(ll). The oxidation process was inhibited in the presence of other ions, and the inhibitive effect was in the following order: Co(ll) < Mo(Vl) < Cd(ll) < Zn(ll) < Ti(IV) < V(V). In the case of hydrocarbons, the efficiencies were as follows: gasoline > benzene > kerosene. The oxidation of sulphur in sulphur-loaded soils obtained from near a textile mill and a distillery were also carried out in the c both cases was significantly enhanced.
Introduction
As an essential natural element, sulphur is required b y plants, animals and man for protein synthesis. But sulphur is now a significant environmental pollutant because of anthropogenic sources and processes which have added additional pathways to those naturally established. These sources now contribute about half as much as nature to the total atmospheric load (Moss, 1976). By 2000 AD it is estimated that in the northern hemisphere alone anthropogenically produced quantities will equal natural production (Kellog, 1972). In 1976, about 50 million tonnes of sulphur was produced, most of which was used to manufacture sulphuric acid (Meyer, 1977). Approximately 7 tonnes of sulphur-waste was discharged per thousand tonnes of sulphuric acid manufactured, which contained as high as 66% of elemental sulphur (Nair et al., 1988). In the spent-wash, the presence of total sulphur has been reported to be 3.52 g L-z, 46.3% of which was as sulphate, and remaining either as elemental sulphur or in other forms (Banerjee, 1989). Each litre of alcohol manufactured produces 10-15 L of spent-wash, and with a discharge of over 12,000 million litres of spent-wash each year in India, the discharge of s u l p h u r ( c o m b i n e d and e l e m e n t a l ) in the environment can be visualised (Sastry, 1985; Iyenger, 1986). The soils polluted by textile mill effluent have been found to contain as high as 3.65% sulphur, 42.2% of which was as sulphate (Pervez et al., 1992). The sulphur so released in the environment joins the natural sulphur cycle of nature. *To whomall correspondenceshouldbe addressed.
It has been further reported that the sulphur waste in presence of water and sunlight showed a progressive increase in acidity which slowed down as the mixture acquired an acidic nature (Nair, 1990). In the work reported here, the catalytic effects of selected metal ions [Co(II), V(V), Ce(III), Ti(IV), Cr(III), Ni(II), Cu(II), Zn(II), Mo(VI), Cd(II) and Hg(II)], and selected hydrocarbons (benzene, kerosene and gasoline) on the oxidation of elemental sulphur in water has been investigated. Each reaction mixture was buffered with marble powder so that the reaction rate was not retarded by a build-up of acidity in the reaction medium. The progressive increase in the concentrations of Ca(II) and Mg(II) released by the marble on interaction with the generated acidity was estimated by EDTA titration, and this increase was taken as the measure of the extent of the oxidation process. Samples of soils collected from the vicinities of the effluent storage ponds of textile mill and distillery industries, which were earlier found to have a good load of sulphur, were also used to study the catalytic effect. Materials and Methods
Sample collection Three soil samples (500 g each) were collected from the effluent storage ponds of a distillery (located at Kumhari, M.P.), and a textile mill (located at Rajnandgaon, M.P.). The marble was collected from a local source. It was chemically analysed, and its p r i n c i p a l c o n s t i t u e n t s were as follows: Moisture - 0.1%; SiO2 - 1.5%; MgCO3- 39%; CaCO3 - 55%; mixed oxides - 4%. The study of the effects of different catalysts have been carried out as described below: Catalytic effects of metallic compounds: A weighed
52
Oxidisability of environmental sulphur
quantity (5 g) of the analysed sample of marble studies were carried out exactly in the same manner powder was mixed with 250 mL of distilled water. as described earlier, except that the hydrocarbons The pH value (8.10) found was taken as a base for (2 mL each) were used in place of the metallic all reaction mixtures studied here. Eleven beakers compounds. The hydrocarbons formed immiscible were labelled, and weighed quantities (1 m mole) of layers in static conditions; on stirring before taking compounds of metals [sulphates in case of Co(H), out the aliquots, their emulsified state was also Ce(III), Ti(IV), Cr(III), Ni(II), Zn(II), Cd(II), and noticed. The loss due to evaporation of the Hg(II); NaVO3 in case of V(V), and (NH4)2MoO4 hydrocarbons was not taken in to account. The in case of Mo(VI)] were placed in beakers marked relationship between duration and the extent of for these elements. Distilled water (250 mL) was sulphur oxidation has been shown in Figure 1(b). added to each beaker. The oxidation states of the Catalytic effect of Cr(III) on oxidation of sulphur in metals used here have been found to be sufficiently soils: Chromium (III) which exhibited the highest stable under the conditions of the experiment influence on the oxidation process of sulphur has (Cotton and Wilkinson, 1967). After stirring, the pH been chosen here to examine its response in the of the solutions was measured, and their values oxidation process of sulphur present in soils. For adjusted to 8.10 which was earlier determined as the this purpose, samples of sulphur-loaded soils base value of the reaction medium. A dilute solution collected from the vicinities of the storage ponds of of NaOH was used for pH adjustment. distillery and textile mill effluents were used. Both Thereafter, weighed quantities (1 g each) of the samples belonged to medium black, heavy clay sulphur powder, 1 0 0 - m e s h size, and weighed soil with 50-55% clay, locally known as Kanhar quantities (5 g each) of analysed sample of marble type. The soils were moderately rich in organic powder (100-mesh size)were added and mixtures matter and fairly well drained. stirred. A l i q u o t s (5 mL each) of the clear The total sulphur and that as sulphate were supernatant solution were drawn from each reaction determined by the gravimetric method in the mixture, filtered using Whatman No.42, and the composited soil samples collected from these two c o n c e n t r a t i o n s of C a ( I I ) a n d M g ( I I ) were sources. For total sulphur, the moisture-free determined titrimetrically using standard solution weighed amounts of samples were heated with a (0.01 M) of EDTA, NH3/NH4C1 solution as buffer fusion mixture of KOH and KNO3 (8:1 by weight), (pH 10) and E r i o c h r o m e Black T (0.4% in and the s u l p h a t e f o r m e d was e s t i m a t e d methanol) as indicator 30 mg of KCN, and the same gravimetrically using BaC12 solution (Treadwell and amount of hydroxylammonium chloride were added Hall, 1958). For the estimation of sulphur present as to the solution before the titration to mask the metal sulphate in the soils, the weighed quantities of ions other than Ca(H) and Mg(II) and to reduce any samples were boiled with dilute hydrochloric acid Fe(III) to Fe(II) to facilitate its masking by the (1:10) and sulphate was determined in the extract cyanide ions (Bassett et aL, 1978). The accuracy of gravimetrically using BaC12 solution (Bassett et al., the method was determined by using an analysed 1978). The values were found as follows: sample of limestone supplied by Bureau of (1) D i s t i l l e r y e f f l u e n t p o l l u t e d soil: Analysed Samples Ltd., Yorks (UK). The percent S(Total) - 3.52% (46.3% of this as sulphate) error in five replicate determinations was found to (2) Textile effluent polluted soil: S(Total) - 3.65% be within 0.8%. (42.2% of this as sulphate) The measurements in each case were carried Two sets of reaction mixtures, one with Cr(III) out at intervals of 24 hours for a duration of 8 days. as catalyst and the other without the catalyst, were All reaction mixtures were maintained at 20°C, and used. Weighed quantities (10 g each) of powdered alsd exposed to sunlight during the day time. The samples of the polluted soils were placed in beakers, volumes of the reaction mixtures were maintained and weighed quantities (5 g each) of marble powder at their initial values by adding distilled water up to and 1 millimole of Cr(III) in the form of its sulphate the marked level in each reaction vessel. The were added to each. Blank reaction mixtures for reaction mixtures were stirred each day before each soil sample using all constituents except the taking out aliquots for analysis. The pH was also catalyst, were also prepared. The other details of the checked each day with a digital pH meter after experiment were the same as described earlier. The stirring and values were found to be static within + measurements were carried out at intervals of 24 hrs 0.02 unit. A blank, without using any catalyst was for a duration of 8 days, and the relationship also run. The relationship between duration (in between the duration and the progress of the days) and the progress of the oxidation reaction, in oxidation reaction has been shown in Figure l(c). terms of volume (in mL) of EDTA solution used has b e e n shown in Figure l(a). The formation of Results and Discussion sulphate was experimentally confirmed in each reaction mixture. Any presence of sulphur as It has been found that many metal ions used here sulphide was also examined and it was found to be have catalytically enhanced the oxidation process of absent in the mixtures. The respective catalysts elemental sulphur. Their catalytic efficiencies have added were found to be present in their ionic state been found in the following order: Cr(III) > Ce(III) in the mixtures. > Cu(II) > Hg(II) > NI(II). Some metal ions on the Catalytic effects of hydrocarbons: The oxidation other hand, have been found to inhibit the oxidation
Namrata Shukla and G.S. Pandey
53
(a)
5 ,o
m s a From Textile mill area
3 .....
Sell (Blank)
M
.
.
.
.
.
.
.
.
1 Sell (Blank) v
0
l
M4
Gasoline i
~E
3-
Benzene Kerosine Blank
(b)
o ¢o
0 L) c 0 o
o @
I
l
0 Cr(IIl)
7
Ce(IIl)
(c)
CuOD ....~
HgCII) Ni(II) Blank
Co(ID Mo(vD
Cd(II) Zn(ID TI(W) V(V)
0 I
3
5 Duration (days)
I
I
7
9 )
Figure 1 Influence of catalysts on oxidation rates of sulphur." (a) Elemental sulphur in presence of metallic elements in different oxidation states; (b) Elemental sulphur in presence of different hydrocarbons; (c) Sulphur in polluted soils in presence of Cr(III).
54
Oxidisability of environmental sulphur
process, and the inhibitive effect was in the following order: Co(II) < Mo(VI) < Cd(II) < ZN(II) < Ti(IV) < V(V). All the hydrocarbons used here have been found to enhance the oxidation process, and their efficiencies were in the following order: gasoline > benzene > kerosene. When examined in the sulphur- loaded soils, it was found that Cr(III), as catalyst, significantly increased the oxidation process of sulphur in both samples of these soils which were polluted by distillery and textile mill effluents. When viewed in overall environmental context, it can be seen that the catalytic metals (Cr, Ce, Cu, Ni, etc.) and the h y d r o c a r b o n molecules a r e commonly introduced into the atmosphere through stack emission and will catalyse the oxidation of the airborne sulphur and thus be promotive to acid-rain formations. Similarly, these metals which are invariably present at trace-levels in surface soils will promote the oxidation of sulphur in the soil- matrix, and this process will be abruptly enhanced in areas where the soils have received excessive load of sulphur through the discharge of industrial wastes. Low soil pH, high soil-salinity and enhanced sulphate levels in the underground water are the logical predictions in areas receiving excessive sulphur.
Acknowledgements One of the authors (N.S.) is grateful to Ravishankar University Raipur for providing financial assistance and experimental facilities.
(PhD Thesis), Ravishankar University, Raipur. Bassett, J., Denney, R.C., Jeffery, G.H. and Mendham, J. 1978. Vogel' s textbook of quantitative inorganic analysis, 4th edn. English Language Book Society, Longman, Essex. Cotton, A.F. and Wilkinson, G. 1967. Advanced inorganic chemistry, 2nd edn. Interscience Publishers, John Wiley, New York. Iyenger, L., Tare, V. and Venkobachar, C. 1986. Comparative evaluation of different support media in attached growth anaerobic treatment of distillery waste. IA WPC Technical Annual, 13, 61-68. Kellog, W.W. 1972. The sulphur cycle. Science, 175, 578-96. Meyer, B. 1977. Sulphur, energy and environment, p.293. Elsevier Scientific Publishing, Company, New York. Moss, M.R. 1976. Biological cycles as integrative and spatial models for the study of environmental pollution - The example of sulphur cycle. Int. J. Environ. Studies, 9, 210. Nair, S. and Pandey, G.S. 1988. Screening of sulphur sludge of sulphuric acid plant for pollutants. Ind. J. Environ. Protection, 8(7), 491-93. Nair, S. and Pandey, G.S. 1990. Acidity generation by sulphur waste of a sulphuric acid plant. Ind. J. Environ. Health, 32(3), 293-295. Pervez, S. and Pandey, G.S. 1992. Some specific characteristics of textile mill effluents and their impacts on soil and ground water. Water Research (Paper communicated). Treadwell, F.P. and Hall, W.T. 1958. Analytical Chemistry, Vol.II. John Wiley, New York.
References Banerjee, D. 1989. Study of environmental impacts of some gaseous; liquid and particulate pollutants
(ManuscriptNo.277; receivedMay 27, 1992 and acceptedafter revision November20, 1992.)
Oxidisability of environmental sulphur under different catalytic conditions Namrata Shukla and G,S, Pandey*
Department of Chemistry, Ravishankar University, Raipur, M.P. 492 010, India Abstract The oxidation of elemental sulphur in the catalytic presence of selected metal ions [Cr(lll), Ce(lll), Cu(ll), Hg(ll), Ni(ll), Co(ll), Mo(Vl), Cd(ll), Zn(ll), Ti(IV), and V(V)], and hydrocarbons (benzene, gasoline, and kerosene) was studied in an alkaline medium buffered by marble powder. The catalytic efficiencies of metal ions were: Cr(lll) > Ce(lll) > Cu(ll) > Hg(ll > Ni(ll). The oxidation process was inhibited in the presence of other ions, and the inhibitive effect was in the following order: Co(ll) < Mo(Vl) < Cd(ll) < Zn(ll) < Ti(IV) < V(V). In the case of hydrocarbons, the efficiencies were as follows: gasoline > benzene > kerosene. The oxidation of sulphur in sulphur-loaded soils obtained from near a textile mill and a distillery were also carried out in the c both cases was significantly enhanced.
Introduction
As an essential natural element, sulphur is required b y plants, animals and man for protein synthesis. But sulphur is now a significant environmental pollutant because of anthropogenic sources and processes which have added additional pathways to those naturally established. These sources now contribute about half as much as nature to the total atmospheric load (Moss, 1976). By 2000 AD it is estimated that in the northern hemisphere alone anthropogenically produced quantities will equal natural production (Kellog, 1972). In 1976, about 50 million tonnes of sulphur was produced, most of which was used to manufacture sulphuric acid (Meyer, 1977). Approximately 7 tonnes of sulphur-waste was discharged per thousand tonnes of sulphuric acid manufactured, which contained as high as 66% of elemental sulphur (Nair et al., 1988). In the spent-wash, the presence of total sulphur has been reported to be 3.52 g L-z, 46.3% of which was as sulphate, and remaining either as elemental sulphur or in other forms (Banerjee, 1989). Each litre of alcohol manufactured produces 10-15 L of spent-wash, and with a discharge of over 12,000 million litres of spent-wash each year in India, the discharge of s u l p h u r ( c o m b i n e d and e l e m e n t a l ) in the environment can be visualised (Sastry, 1985; Iyenger, 1986). The soils polluted by textile mill effluent have been found to contain as high as 3.65% sulphur, 42.2% of which was as sulphate (Pervez et al., 1992). The sulphur so released in the environment joins the natural sulphur cycle of nature. *To whomall correspondenceshouldbe addressed.
It has been further reported that the sulphur waste in presence of water and sunlight showed a progressive increase in acidity which slowed down as the mixture acquired an acidic nature (Nair, 1990). In the work reported here, the catalytic effects of selected metal ions [Co(II), V(V), Ce(III), Ti(IV), Cr(III), Ni(II), Cu(II), Zn(II), Mo(VI), Cd(II) and Hg(II)], and selected hydrocarbons (benzene, kerosene and gasoline) on the oxidation of elemental sulphur in water has been investigated. Each reaction mixture was buffered with marble powder so that the reaction rate was not retarded by a build-up of acidity in the reaction medium. The progressive increase in the concentrations of Ca(II) and Mg(II) released by the marble on interaction with the generated acidity was estimated by EDTA titration, and this increase was taken as the measure of the extent of the oxidation process. Samples of soils collected from the vicinities of the effluent storage ponds of textile mill and distillery industries, which were earlier found to have a good load of sulphur, were also used to study the catalytic effect. Materials and Methods
Sample collection Three soil samples (500 g each) were collected from the effluent storage ponds of a distillery (located at Kumhari, M.P.), and a textile mill (located at Rajnandgaon, M.P.). The marble was collected from a local source. It was chemically analysed, and its p r i n c i p a l c o n s t i t u e n t s were as follows: Moisture - 0.1%; SiO2 - 1.5%; MgCO3- 39%; CaCO3 - 55%; mixed oxides - 4%. The study of the effects of different catalysts have been carried out as described below: Catalytic effects of metallic compounds: A weighed
52
Oxidisability of environmental sulphur
quantity (5 g) of the analysed sample of marble studies were carried out exactly in the same manner powder was mixed with 250 mL of distilled water. as described earlier, except that the hydrocarbons The pH value (8.10) found was taken as a base for (2 mL each) were used in place of the metallic all reaction mixtures studied here. Eleven beakers compounds. The hydrocarbons formed immiscible were labelled, and weighed quantities (1 m mole) of layers in static conditions; on stirring before taking compounds of metals [sulphates in case of Co(H), out the aliquots, their emulsified state was also Ce(III), Ti(IV), Cr(III), Ni(II), Zn(II), Cd(II), and noticed. The loss due to evaporation of the Hg(II); NaVO3 in case of V(V), and (NH4)2MoO4 hydrocarbons was not taken in to account. The in case of Mo(VI)] were placed in beakers marked relationship between duration and the extent of for these elements. Distilled water (250 mL) was sulphur oxidation has been shown in Figure 1(b). added to each beaker. The oxidation states of the Catalytic effect of Cr(III) on oxidation of sulphur in metals used here have been found to be sufficiently soils: Chromium (III) which exhibited the highest stable under the conditions of the experiment influence on the oxidation process of sulphur has (Cotton and Wilkinson, 1967). After stirring, the pH been chosen here to examine its response in the of the solutions was measured, and their values oxidation process of sulphur present in soils. For adjusted to 8.10 which was earlier determined as the this purpose, samples of sulphur-loaded soils base value of the reaction medium. A dilute solution collected from the vicinities of the storage ponds of of NaOH was used for pH adjustment. distillery and textile mill effluents were used. Both Thereafter, weighed quantities (1 g each) of the samples belonged to medium black, heavy clay sulphur powder, 1 0 0 - m e s h size, and weighed soil with 50-55% clay, locally known as Kanhar quantities (5 g each) of analysed sample of marble type. The soils were moderately rich in organic powder (100-mesh size)were added and mixtures matter and fairly well drained. stirred. A l i q u o t s (5 mL each) of the clear The total sulphur and that as sulphate were supernatant solution were drawn from each reaction determined by the gravimetric method in the mixture, filtered using Whatman No.42, and the composited soil samples collected from these two c o n c e n t r a t i o n s of C a ( I I ) a n d M g ( I I ) were sources. For total sulphur, the moisture-free determined titrimetrically using standard solution weighed amounts of samples were heated with a (0.01 M) of EDTA, NH3/NH4C1 solution as buffer fusion mixture of KOH and KNO3 (8:1 by weight), (pH 10) and E r i o c h r o m e Black T (0.4% in and the s u l p h a t e f o r m e d was e s t i m a t e d methanol) as indicator 30 mg of KCN, and the same gravimetrically using BaC12 solution (Treadwell and amount of hydroxylammonium chloride were added Hall, 1958). For the estimation of sulphur present as to the solution before the titration to mask the metal sulphate in the soils, the weighed quantities of ions other than Ca(H) and Mg(II) and to reduce any samples were boiled with dilute hydrochloric acid Fe(III) to Fe(II) to facilitate its masking by the (1:10) and sulphate was determined in the extract cyanide ions (Bassett et aL, 1978). The accuracy of gravimetrically using BaC12 solution (Bassett et al., the method was determined by using an analysed 1978). The values were found as follows: sample of limestone supplied by Bureau of (1) D i s t i l l e r y e f f l u e n t p o l l u t e d soil: Analysed Samples Ltd., Yorks (UK). The percent S(Total) - 3.52% (46.3% of this as sulphate) error in five replicate determinations was found to (2) Textile effluent polluted soil: S(Total) - 3.65% be within 0.8%. (42.2% of this as sulphate) The measurements in each case were carried Two sets of reaction mixtures, one with Cr(III) out at intervals of 24 hours for a duration of 8 days. as catalyst and the other without the catalyst, were All reaction mixtures were maintained at 20°C, and used. Weighed quantities (10 g each) of powdered alsd exposed to sunlight during the day time. The samples of the polluted soils were placed in beakers, volumes of the reaction mixtures were maintained and weighed quantities (5 g each) of marble powder at their initial values by adding distilled water up to and 1 millimole of Cr(III) in the form of its sulphate the marked level in each reaction vessel. The were added to each. Blank reaction mixtures for reaction mixtures were stirred each day before each soil sample using all constituents except the taking out aliquots for analysis. The pH was also catalyst, were also prepared. The other details of the checked each day with a digital pH meter after experiment were the same as described earlier. The stirring and values were found to be static within + measurements were carried out at intervals of 24 hrs 0.02 unit. A blank, without using any catalyst was for a duration of 8 days, and the relationship also run. The relationship between duration (in between the duration and the progress of the days) and the progress of the oxidation reaction, in oxidation reaction has been shown in Figure l(c). terms of volume (in mL) of EDTA solution used has b e e n shown in Figure l(a). The formation of Results and Discussion sulphate was experimentally confirmed in each reaction mixture. Any presence of sulphur as It has been found that many metal ions used here sulphide was also examined and it was found to be have catalytically enhanced the oxidation process of absent in the mixtures. The respective catalysts elemental sulphur. Their catalytic efficiencies have added were found to be present in their ionic state been found in the following order: Cr(III) > Ce(III) in the mixtures. > Cu(II) > Hg(II) > NI(II). Some metal ions on the Catalytic effects of hydrocarbons: The oxidation other hand, have been found to inhibit the oxidation
Namrata Shukla and G.S. Pandey
53
(a)
5 ,o
m s a From Textile mill area
3 .....
Sell (Blank)
M
.
.
.
.
.
.
.
.
1 Sell (Blank) v
0
l
M4
Gasoline i
~E
3-
Benzene Kerosine Blank
(b)
o ¢o
0 L) c 0 o
o @
I
l
0 Cr(IIl)
7
Ce(IIl)
(c)
CuOD ....~
HgCII) Ni(II) Blank
Co(ID Mo(vD
Cd(II) Zn(ID TI(W) V(V)
0 I
3
5 Duration (days)
I
I
7
9 )
Figure 1 Influence of catalysts on oxidation rates of sulphur." (a) Elemental sulphur in presence of metallic elements in different oxidation states; (b) Elemental sulphur in presence of different hydrocarbons; (c) Sulphur in polluted soils in presence of Cr(III).
54
Oxidisability of environmental sulphur
process, and the inhibitive effect was in the following order: Co(II) < Mo(VI) < Cd(II) < ZN(II) < Ti(IV) < V(V). All the hydrocarbons used here have been found to enhance the oxidation process, and their efficiencies were in the following order: gasoline > benzene > kerosene. When examined in the sulphur- loaded soils, it was found that Cr(III), as catalyst, significantly increased the oxidation process of sulphur in both samples of these soils which were polluted by distillery and textile mill effluents. When viewed in overall environmental context, it can be seen that the catalytic metals (Cr, Ce, Cu, Ni, etc.) and the h y d r o c a r b o n molecules a r e commonly introduced into the atmosphere through stack emission and will catalyse the oxidation of the airborne sulphur and thus be promotive to acid-rain formations. Similarly, these metals which are invariably present at trace-levels in surface soils will promote the oxidation of sulphur in the soil- matrix, and this process will be abruptly enhanced in areas where the soils have received excessive load of sulphur through the discharge of industrial wastes. Low soil pH, high soil-salinity and enhanced sulphate levels in the underground water are the logical predictions in areas receiving excessive sulphur.
Acknowledgements One of the authors (N.S.) is grateful to Ravishankar University Raipur for providing financial assistance and experimental facilities.
(PhD Thesis), Ravishankar University, Raipur. Bassett, J., Denney, R.C., Jeffery, G.H. and Mendham, J. 1978. Vogel' s textbook of quantitative inorganic analysis, 4th edn. English Language Book Society, Longman, Essex. Cotton, A.F. and Wilkinson, G. 1967. Advanced inorganic chemistry, 2nd edn. Interscience Publishers, John Wiley, New York. Iyenger, L., Tare, V. and Venkobachar, C. 1986. Comparative evaluation of different support media in attached growth anaerobic treatment of distillery waste. IA WPC Technical Annual, 13, 61-68. Kellog, W.W. 1972. The sulphur cycle. Science, 175, 578-96. Meyer, B. 1977. Sulphur, energy and environment, p.293. Elsevier Scientific Publishing, Company, New York. Moss, M.R. 1976. Biological cycles as integrative and spatial models for the study of environmental pollution - The example of sulphur cycle. Int. J. Environ. Studies, 9, 210. Nair, S. and Pandey, G.S. 1988. Screening of sulphur sludge of sulphuric acid plant for pollutants. Ind. J. Environ. Protection, 8(7), 491-93. Nair, S. and Pandey, G.S. 1990. Acidity generation by sulphur waste of a sulphuric acid plant. Ind. J. Environ. Health, 32(3), 293-295. Pervez, S. and Pandey, G.S. 1992. Some specific characteristics of textile mill effluents and their impacts on soil and ground water. Water Research (Paper communicated). Treadwell, F.P. and Hall, W.T. 1958. Analytical Chemistry, Vol.II. John Wiley, New York.
References Banerjee, D. 1989. Study of environmental impacts of some gaseous; liquid and particulate pollutants
(ManuscriptNo.277; receivedMay 27, 1992 and acceptedafter revision November20, 1992.)
